1. Field of the Invention
The invention relates generally to method and apparatus for deriving hydrocarbon indications underwater and, more particularly, but not by way of limitation, it relates to improved detection methods for locating oil presence and seep sources on the sea floor and within a body of water.
2. Description of the Prior Art
The prior art includes numerous systems that are utilized for actively detecting the presence of hydrocarbons such as result from oil spills and the like on the surface of both earth and water. Such prior art systems have utilized microwave radiation, ultra violet illumination, laser beams and the like to initiate key responses which are then scanned from remote positions, such as an airborne platform. Some representative U.S. Patents falling in this category are U.S. Pat. Nos. 3,899,213, Fantasia, et al.; 3,961,187, Barringer; and, 3,736,428, Monroe. These prior active systems all function to detect reflectance, luminescence, or emittance characteristics of oil on the water surface and such systems necessarily operate from a remote platform such as an airborne vehicle or water vessel.
Direct detection of oil or other hydrocarbon products below the sea surface has been carried out heretofore by means of geochemical prospecting techniques. One technique involves the detection of hydrocarbon seepage through the analysis of hydrocarbons dissolved in sea water. Another technique relies on the analysis of bottom sediment samples for their hydrocarbon content. The sea water sampling method requires very sensitive analytical techniques because the hydrocarbon gases dissolved in sea water are rapidly dispersed by marine currents. Bottom sediment analysis applies the same principles that govern soil sediment prospecting on land surface. The sampling is generally at least two or four meters beneath the sea bottom in order to avoid contamination by organic matter at or near the bottom, and accumulated samples are then treated with acids while liberated hydrocarbon gases are analyzed by gas chromatograph or the like. None of the prior methods readily provide an accurate indication of the position of the source of seepage on the ocean floor. Moreover, hydrocarbon gas concentrations in water or bottom sediments may originate from sources other than subsurface hydrocarbon deposits or pipelines, such as decomposition of organic matter.